Try to see which fingerings work for you. Some people play it with B, G, F, and D main stack keys pressed down....others like myself use Fork F, regular F, and side Bb pressed down.
No matter what, always work out the sequence when you're playing the G...it's a much different beast to simply "play an alt. G" than to build into the with the phrase.
Just remember that it needs to be strong, clear, and in tune. That G is the climax of that entire section, and arguably of the entire movement. It needs to be powerful and moving.
Good luck!
Saxaholic